000
FXUS61 KOKX 181745
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
145 PM EDT Sun Mar 18 2018
.SYNOPSIS...
Weak low pressure and cold front approach today and pass
tonight. High pressure builds down from southern Canada through
Monday night. A series of lows will pass to the south from
Tuesday into Wednesday night, followed by high pressure
building down from central Canada for the rest of this week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...

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Dew points continue to run several degrees below previous
forecast levels as mixing, and gusty winds, continue bringing
in drier air. Otherwise forecast remains on track through this
afternoon.
A weak surface low was now moving into the eastern Great Lakes
and into western upstate NY. This low along with an upper
shortwave passing from NW to SE across New England and into the
region will have little apparent effect until tonight.

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&&
.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
Another upper level shortwave passes just to the north tonight
as a weak area of low pressure and frontal boundary move through
overnight. Very low probability for a few flurries, with
operational GFS only model hinting at a few flurries.
Mostly clear skies give way to partly cloudy conditions as these
weak disturbances move through.
High pressure builds from the north Monday, but remains centered
in Canada as it is blocked by mid west shortwave tracking from
west to east. During this time frame, mainly clear skies are
forecast, along with chilly temperatures as cold Canadian air
remains.
Lows each night range from the upper teens to the lower 30s in
NYC. During the day Monday, mos consensus forecasts a range from
the upper 30s to middle 40s, which seems reasonable given cold
temps aloft.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
Very complex and uncertain scenario going into this time frame
as multiple shortwave troughs interact to form a series of
surface lows that could impact the area. Some of this energy
will be coming from (1) the subtropical Pacific, (2) a cutoff
low over the western CONUS, (3) another cutoff low farther west
over the Pacific, and (4) additional shortwaves dropping down
from central Canada. Complicating matters further will be the
confluence of northern/southern streams situated over or just
north of the area. Models are converging on a general solution
of energy from (1) and (2) combining to help form an initial sfc
low that should eject off the southern Mid Atlantic coast on
Tuesday, then phasing of (3) and (4) to form a second stronger
low that should also pass off the Mid Atlantic coast on Wed.
Given model tendency (especially in the GFS) to overdo the
confluence zone and suppress sfc lows too far south, also
somewhat favorable coupling of two upper jet streaks, one
associated with the confluence zone and another with the
approaching western energy, think chances for snow could exist
occur farther north with both rounds than operational model
forecasts suggest, with the combo of the 00Z NAM/03Z SREF mean
capturing this idea pretty well for the first low. With that in
mind, have forecast chance PoP with the first wave for NYC metro
and Long Island for daytime Tue, and then likely PoP for Long
Island and chance elsewhere on Wed. Despite fcst high temps, sfc
wet bulb temps should be cold enough to support all snow.
One thing that remains fairly consistent regardless of solution
is that it will be at least brisk to windy from late Tuesday
into Thursday - potentially rather gusty depending on exact
track/strength of the coastal low(s).
The axis of the SE Canada cutoff passes to the east Thursday
night, but with dry low levels, it should be dry. Friday and
Friday night should be dry as northern stream ridging transits
the area.
For now went dry on Saturday as a cutoff low builds to the
north, and it appears that the next batch of moisture/lift
holds off until later in the weekend.
Temperatures are forecast to be below normal.
&&
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...

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High pressure will build to the north. A weakening low will
pass across the region tonight.
VFR through the TAF period. NW winds today around 10kt will gust
to around 20-25kt through about 22Z. Gusts then diminish and
winds fall below 10kt, eventually becoming light and variable
overnight. On Monday, winds increase from the North to around
10kt, then become Northwest by mid to late morning.
.OUTLOOK FOR 18Z MONDAY THROUGH THURSDAY...
.Monday afternoon and Monday night...VFR.
.Tuesday...Low confidence forecast through Wednesday. Chance of
snow with IFR conditions for the Long Island and NYC Metro
terminals. ENE winds G20KT NYC metro/coastal terminals.
.Tuesday night...MVFR conditions possible with any lingering
snow showers. NE winds G20KT NYC metro/coastal terminals, mainly
late.
.Wednesday...Snow with IFR conds likely at the Long Island
terminals, and may also be possible farther north including all
local terminals. NE winds G20-25KT.
.Thursday-Friday...VFR. N winds G15-20KT.

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&&
.MARINE...

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Marginal SCA conditions remain across the ocean waters and into
the Great South Bay as nearshore, and ocean water, gusts were
just below small craft. Ocean seas have been just under SCA
levels, but were fluctuating. Will continue with the advisory,
and may end up canceling with the afternoon forecast.
Winds continue to diminish tonight and into Monday as high
pressure builds in from the north.
Seas remain 4 ft or less on the ocean and 2 ft or less on non
ocean waters tonight through Monday night. However, cannot
completely rule out 5 footers over the eastern ocean waters late
in the day due to an increase in northerly winds.
The pressure gradient should tighten Tuesday and remain
moderate to strong in strength into Thursday. SCA conditions
probably develop on the coastal ocean waters Tuesday and on the
remainder of the waters Tuesday night. SCA conditions probably
will continue into at least Wednesday night, with gales possible
on the ocean from late Tue night into Wed evening.
Conditions should gradually fall below SCA levels on Thursday.

-- End Changed Discussion --

&&
.HYDROLOGY...
A low probability for significant precipitation exists Tuesday
through Wednesday night depending on the eventual track of low
pressure centers. If precipitation does indeed occur, it likely
will be in the form of snow, so no hydrologic impacts are
anticipated.
&&
.TIDES/COASTAL FLOODING...
There is the potential for a prolonged period of E-NE flow from
Monday night into Wednesday Night. Tidal departures of
generally only 1 to 1 1/2 ft are needed for minor flooding for
many locations during this time, and 2 to 3 ft for moderate.
Depending on the exact track/strength of a coastal low or lows
during this time frame, there is the potential for minor to
moderate coastal flooding, but predictability on the details
remains low.
&&
.EQUIPMENT...
NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the
air for an extended period of time.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 4 PM EDT this afternoon for ANZ345-
350-353-355.
&&
$$
SYNOPSIS...Goodman/PW
NEAR TERM...19
SHORT TERM...PW
LONG TERM...Goodman
AVIATION...BC
MARINE...Goodman/19/PW
HYDROLOGY...Goodman/PW
TIDES/COASTAL FLOODING...
EQUIPMENT...